The yen weakened for a second day on Thursday, with the US dollar breaking a new four-year high within two days as investors sold off the Japanese currency in the wake of Bank of Japan stimulus measures.

USDJPY got so close to the key 100 yen level and hit 99.93 in the late US session.The pair has rallied 7 percent since the BoJ pledged at its policy meeting last week to inject about $1.4 trillion into the Japanese economy to fight deflation and achieve its 2 percent inflation target.

EURJPY rose to the highest level in more than three years, hitting 131.11 yen, up 0.5 percent on the day.

The yen was especially weaker against higher-yielding currencies, such as Australian and New Zealand dollars, as this makes a good carry trade, where investors borrow in yen cheaply and use the proceeds to invest in such higher-yielding currencies.

Aussie surged to a five-and-a-half year high against the yen at 105.41 while the kiwi hit 86.38 today, its strongest since early 2008.

Against the dollar, the euro hovered at the highs of the day $1.3166 after being lifted by a successful Italy 3-year debt auction today that reduced borrowing costs. This the highest level the euro has reached since the end of February.

GBPUSD hit a 7-week high of $1.5410, up from a low of $1.5318.

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